Adding time and date to a filename - c

Question

I'm trying to write a source file, that would take in the filename/directory and then add current date & time to the end of the file name. So far I've found out that we can use the time() & localtime() functions. However, I'm not quite sure on where to start.
Could someone give me some instructions/steps on the path I could follow to get there?
Thanks! :D

Answer 1

Use time() and localtime() to get the current time
Use strftime() to format it to the format you want.
Use snprintf() to combine the formatted time with the original file name.
Use rename() to do the actual renaming.
Note that all of the above can be done in one line of shell script, so ask yourself whether you really need to do it in C, as opposed to relegating it to sh.

Answer 2

To get the date/time you have to include time.h.
Then you can use the localtime function like this:
time_t t = time(NULL);
struct tm tm = *localtime(&t);
The struct tm contains the desired information. You can access the day of the month by tm.tm_mday and so on.
You can use sprintf to write all the date information to a string like this:
char datum[128];
sprintf(datum, "%d-%d-%dT%d:%d:%d", tm.tm_year+1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec);
printf("%s\n", datum);
would give something like
2013-10-31T20:26:42
You can append this string to your filename by using strcat

Answer 3

This code will work.
char timestr[50];
time_t now = time(NULL);
struct tm *t = localtime(&now);
strftime(timestr, sizeof(timestr)-1, "%m-%d-%Y", t);
timestr[49] = 0;
if((filename = malloc(strlen(argv[2])+strlen(timestr)+1) != NULL) {
filename[0] = '\0';
strcat(filename,argv[2];
strcat(filename,"_");
strcat(filename,timestr);
strcat(filename,".log");
}
Just change the argv[2] as per your code argc.